Damper assembly for air mixers



Feb. 16, 1965 w. w. KENNEDY DAMPER ASSEMBLY FOR AIR MIXERS 3Sheets-Sheet 1 Original Filed March 16, 1961 mavalo Q'k/ Walt e Qf G m'La, M wn QA'r-rommav/ Feb. 16, 1965 w. w. KENNEDY DAMPER ASSEMBLY FOR AIRMIXERS Original Filed March 16 3 Sheets-Sheet 2 United States Patent OfiRe. 25,729 Reissued Feb. 16, 1965 25,729 DAMPER ASSEMBLY FOR AIR MIXERSWalter W. Kennedy, Rockford, Ill., assignor to Barber- Colman Company,Rockford, Ill., acorporation of Illinois Original No. 3,123,097, datedMar. 3, 1964, Ser. No. 96,208, Mar. 16, 1961. Application for reissueApr. 27, 1964, Ser. No. 377,150

' 10 Claims. (Cl. 137601) Matter enclosed in heavy brackets appears inthe;

original patent but forms no part of this reissue specification; matterprinted in italics indicates the additions made by reissue. Y

This invention relates to a damper for regulating the flow of air orother gas through a duct and has more particular reference to a damperin which the air flow is controlled by expanding or contracting a coneor umbrella-like device to vary the radial width of an annular openingwithin the duct. A conical damper of this character forms the subjectmatter of Patent 3,070,346.

In such dampers, the cone is pointed downstream and, when of the properangle and properly sized in relation to the duct, effects asubstantially uniform distribution of the air across the entiredownstream cross-section of the duct beyond the damper and through anadjacent discharge outlet even though the flow may be confined to anarrow radial width when the damper is only partially open. Thisdesirable action is attributable to the negative pressure which developsbeyond the cone and within the annular orifice and which draws part ofthe air stream inwardly along the converging surface of the cone. It hasbeen found that such drawing of the air inwardly is limited to a certainsize of cone.

The primary object of the present invention is to adapt a cone damper ofthe above character to ducts of larger size while maintaining evendistribution of the air across, the area of the duct beyond the cone.

A more detailed object is to divide the duct into a plurality ofconcentric annular orifices or passages and regulating the flowsthercthrough by separate cone dampers.

The invention also resides in the novel manner of mounting and actuatingthe several dampers in unison.

Other objects and advantages of the present invention will becomeapparent from the following detailed description taken in connectionwith the accompanying drawings, in whichi v FIGURE 1 is a diametricalsectional view of an air duct and damper embodying the presentinvention, the

parts being shown in closed positions.

FIG. 2 is a fragmentary perspective view looking to ward the downstreamend of the damper.

FIG. 3 is a fragmentary sectional view similar to FIG. 1 showing thedamper fully opened.

FIG. 4 is a perspective view of the inner umbrella.

FIGS. 5 and 6 are sectional views taken respectively along the lines 5-5and 66 in FIG. 3.

FIGS. 7 and 8 are diagrammatic views illustrating the distribution ofair flow with the damper opened different degrees.

For controlling the flow of airthrough a duct 10 a damper embodying theinvention is mounted within the duct which is divided into two or moreconcentric annular passages 12, 13 selectively variable in width toregulate the total fiow of air past the damper and deliver the airthrough a suitable distribution outlet 8 herein shown as comprising acenter disk and a series of conicentric cones 9. Generally stated, theinvention contemplates making the damper of two or more concentricelements 15, 16 each in the form of an expansible and collapsibletruncated cone or umbrella and correlated in size and shape 'with theouter walls of the passages 12,

v cones,.the passages 12, 13 may be closed tightly (FIG.

. the duct in the direction indicated by the arrows- The apex of eachcone or umbrella is directed downstream .drical nut threaded onto ascrew 30 which is 1) or'partially opened to any desired degree (FIGS. 3,7 and 8) for regulating the total flow of air through so that thepressure of the oncoming air on the upstream inner side 'of the coneelements assists in holding the cones open and assures a tight sealbetween the outer periphery of the cones and the adjacent duct wall whenthe damperis fully expanded (FIG. 1). p v

The outer passage 12 is defined by the duct wall 10 and a ring 17 ofsmaller diameter concentricwith the axis of the duct and" supported,from the latter in an axially fixed. position by angularly spaced spokes18. After insertion of the damper in the duct, flanges 19.0n the outerends of the spokesare secured to the ductby screws 20. The inner endsof, the spokes are rigid with a split collar21 contracted by bolts 22around the ring 17 which herein comprises a short length of metaltubing. The inner wall of the inner passage 13 isdefined by a tubularring 23 substantially smaller than the tube 17 and axially fixedconcentric with the latter by spokes 24. Flanges 25 at opposite ends ofthese spokes are welded 'or otherwise fixed to the downstream ends ofthe rings 17 and 23. For a purpose to appear later, the downstream endof the ring 23 is closed by a wall 23 thus forming a cylindrical cupwhich opens upstream. The outer wall of the inner passage 13 isdefinedby a tubular annulus 26 concentric with and somewhat smaller thanthe ring 17. Herein, the downstream end of the [ring] annulus iscylindrical while the other end is shaped: to form an outwardly openingannular groove 27, this. being defined by flanges 28 in the presentinstance. As will appear later, the space between the outer ring 17 andthe annulus 26 is closed by the inner edge portion of the outer umbrella15. i I

To provide for opening and closing of the outer umbrella, the annulus 26is mounted'for movement axially back and forth along the duct axis.Herein, this is. accomplished by connection of the annulus with anactuator member 29 disposed within the cup 23 and itself mounted foraxial movement relative thereto. For this purpose, the member takes theform of a generally cylinjournaled in the cup bottom 23 and axiallyfixed between a shoulder on the screw and a washer 31 pinned on theouter end of the screw. The latter projects frornthe cup in a directiondownstream of the duct and is slotted as at 32 or otherwise shaped toreceive a tool by which the screw,

may be turned to open and close the umbrella dampers.

The actuating member and the annulus 26 are joined rigidly by angularlyspaced spokes in the form of L- shaped wiresl33 whose long legs aredisposed radially and project into holes 34 in bars 35 which parallelthe duct axis and are welded to the cylindrical part of closed in theabove mentioned application as a molded frusto-conical thin disk 40 offlexible rubber or other suitable plastic in which is embedded duringthe molding a plurality of angulary spaced wire ribs 41. Preferably,though not necessarily, the latter are completely covered by the rubberso as to provide continuous'somewhat yieldable outer edges 42 adapted tocome in full sealing engagement with the outer and'inner duct walls 10and 26 time the air reaches the discharge outlet 8 even though theannulus 26 and thus separate the inner and outer duct passages 12 and13.

At the bends 44 in the ribs, the latter are supported to swing aboutindividual axes disposed substantially tangent to the upstream end ofthe tube 17 and thus providefor opening and closing of the umbrella.,While 7 various fulcrums may be employed, the hinges indicated at 45are formed in the present instance by the rubber at'the junctions of theinner edges of'the umbrella and the end of a sleeve 46 molded integralwith the umbrella at the heels 44 of the ribs and telescopedsubstantially throughout its length around the tube 17. a The sleeve isclamped to the tube by the split collar 21. i

- The rubber covered inner ends 47 of the ribs 41 projectloosely intothe outwardly opening groove 27 in the an nulus 2 6 which groove isshaped to accommodate the full range of axial shifting of the annulusrequired for fully opening and closing the umbrella as shown in' FIGS. 1and 3 In the closing movement from the open position shown in FIG. 1,the rubber'webs between each pair of adjacent ribs bend inwardly andform folds 49 as shown in FIGS. 3, 5 and 6. Y

The inner umbrella 16 is constructed and mounted in the same way and thepartsthereof corresponding to those of the outer umbrella are indicatedby the same but primed numbers. In this instance, the inner ends 47' ofthe ribs 41' project into an outwardly opening groove 50 formed in theupstream end of the nut 29 beyond the lip of the cup 23.

When mounted as above described, it will be apparent that in response toturning of the screw 30 lHMOPPOSllIb' directions, the nut 29 and theannulus 26 rigid therewith will move in unison and axially incorresponding directions. Both umbrellas are correspondingly expandedand collapsed thus correspondingly varying'tne radial widths of theinner and outer passages 12 and 13 therefore the total rate of air flowpast the damper. The arrange-,

ment is such that the outer peripheries 42, and 42' of the umbrellascome into engagement with the duct walls and 26 simultaneously as shownin FIG. 1. 1n the present instance, the short legs of the ribs 41' ofthej inner umbrella are somewhat shorter than the short legs of theouter umbrella so that the ribs 41' swing through a correspondinglygreater'angle in the. movement of the nut through its. full range.

The double coned damper'constructed as described above,

is well suited for use in'ducts ranging from about 8 to 16 inches indiameter. In [the larger of] such ducts the umbrellas 15 and 16 aredisposed at [an] a cone angle of about 20 degrees relative to a planenormal to the duct axis when fully expanded (FIG. 1) against the longandshort outer walls 10 and 26 of the two duct passages 12 and 13. As thedampers start to open and the cone angle is increased to about 23degrees as shown in FIG. 7, the

air flows past the outer edges of the umbrellas in two radially spacedstreams and such division alone effects a desirable distribution of thefiow radially acrossthe duct 10.

There is some bending of these streams, especially the inner one,inwardly to follow the downstream surface of the cones, this beingillustrated by the arrows in FIG. 7.

As the cones are [expanded] contracted further and reach an angle ofabout degrees as shown in RIG. 8,

the negative pressures developed on the downstream sides of the conesbecomes substantially more effective in bending the annular streamsinwardly. Thus, the radial widths of the streams are increased asillustrated by the arrows in FIG. 8, substanti ally the entirecross-sectional area of the duct 10 being, covered by the two expandingstreams bythe the latter is located quite close to the damper as isdesirable in most installations. Such expanding of air streams under thedeveloped negative pressures increases as the cone angles of theumbrellas are further increased so that over the major part of theopening range, the total air flow is distributed substantially uniformlyover the entire area of the discharge outlet.

maxirnum radial width of each annular passage does not exceed about 4inches. In such'cases, full closure of the duct is achieved withoutexpanding the umbrellas very far beyond a 30 degree cone angle which isabout the minimum capable of effectually producing the desired inwardbending of the air streams passing through the respective annularorifies.

I'claim asmy'invention:

l. The combination of, an elongated outer wall, a ring smaller than saidwall and fixedly mounted within said wall concentric with the latter andcooperating therewith to define an outer annular air passage, an annulusshorter than said wall and smaller than said ring and mounted concentricwith the latter for axial shifting, a second smaller ring rigid withsaid wall and said first ring and cooperating with said annulus to forman inner annular air passage concentric with said outer passage, amember rigid with said annulus and mounted within said second ring formovement back and forth along the axis of said rings, a frusto-conicalumbrella disposed in said outer air passage and radially expansible andcontractible to vary the width of said outer passage and thereby controlthe flow of air therethrough, a similar smaller umbrella disposed insaid inner passage and radially expansibleand contractible to controlthe flow of air theretbrough, the peripheral shapes of said umbrellascorrespondingto said :wall and annulus so as to close the passages whenthe umbrellas are expanded against the wall and annulus, and actuatingmeans for moving said member and said annulus back and forth axiallyrelative to said rings to open and close both of said umbrellas inunison.

2. The combination defined in claim 1 in which the plurality ofangularly spaced spokes rigidly joining said" .first andsecondrings.

5. The combination defined in claim 4 including screw and nut elementsone' forrned by said member and relatively rotatable to shift saidmember and said second ring axially relative to each other and therebyopen and close both of said umbrellas. v I

6. The combination as defined in claim 1 in which the cone angles ofsaid inner and outer umbrellas are sub staniially equal.

7. The combination as defined'in claim 1 in which the cone angles ofsaid inner and outer umbrellas areiwithin a range of between l-Gand]approximately 20'degrees when the umbrellas are fully expanded againstsaidwall, said angles increasing progressively during closing of the iumbrellas.

8. The combination as defined in claim 1 in which saidinner and outerumbrellas includeangularly spaced-ribs of generally L-shaped fulcrumcdat the heels of the Us on said first and second rings to swing in radialplanes, and means coupling the inner ends of all of said ribs to saidmember.

9. The combination of, an elongated outer Wall defining an air duct, anaxially fixed ring smaller than said wall and fixedly mounted withinsaid wall concentric with the latter and cooperating therewith to definean outer annular air passage, an axially shiftable annulus shorter thansaid Wall and smaller than said ring, a second axially fixed ringsmaller than and concentric With said annulus and cooperating therewithto form an inner air passage, a member mounted within said second ringfor movement back and forth along the axis of said rings, afrustoconical umbrella disposed in said outer air passage, means on saidfirst ring supporting said umbrella for radial expansion and contractionto control the flow of air through the outer passage, a similar smallerumbrella disposed in said inner passage, means on said second ringsupporting said second umbrella for radial expansion and contraction tocontrol the flow of air through the inner passage,

the outer edges of said umbrellas being shaped to contact said Wall andannulus around the entire peripheries thereof and thereby close both ofsaid passages when the umbrellas are fully opened and means for movingsaid member and said annulus back and forth axially to open and closeboth of said umbrellas in unison.

10. The combination defined in claim 1 in which said outer and innerumbrellas include angularly spaced radially disposed ribs respectivelyfulcrumed adjacent their inner ends on said first and second rings toswing about fixed axes extending tangentially of said rings.

References Cited by the-Examiner The following references, cited by theExaminer, are of record in the patented file of this patent or theoriginal patent.

UNITED STATES PATENTS 2,881,687 4/59 Manor 98l 20 WILLIAM F. ODEA,Primary Examiner.

